| Radiation-hardened Fiber: An optical fiber made
with core and cladding materials that
are designed to recover their intrinsic value
of attenuation coefficient, within an acceptable
time period, after exposure to a radiation pulse. |
| Radiometer: An instrument,
distinct from a photometer, to measure power
(Watts) of electromagnetic
radiation. |
| Radiometry: The science
of radiation measurement. |
| Raman Amplifier: An optical amplifier based on Raman scattering which generates
many different wavelengths of light from a nominally
single-wavelength source by means of lasing
action or by the beating together of two frequencies.
The optical signal can be amplified by collecting
the Raman scattered light. |
| Random Jitter (RJ): Random
jitter is due to thermal noise and may be modeled
as a Gaussian process.
The peak-to-peak value of RJ is of a probabilistic
nature, and thus any specific value requires
an associated probability. |
|
| Rayleigh
Scattering: The scattering of light
that results from small inhomogeneities of material
density or composition. |
| Rays: Lines that represent
the path taken by light. |
| Receiver: A terminal device that includes a detector and signal processing
electronics. It functions as an optical-to-electrical converter. |
 |
| Receiver
Overload: The maximum acceptable
value of average received power for an acceptable BER or performance. |
| Receiver Sensitivity: The minimum
acceptable value of received power needed to
achieve an acceptable BER or performance. It takes
into account power penalties caused by use of
a transmitter with worst-case
values of extinction ratio, jitter, pulse rise
times and fall times, optical return
loss, receiver connector degradations, and
measurement tolerances. The receiver sensitivity
does not include power penalties associated
with dispersion, or backreflections from the optical path; these effects are specified
separately in the allocation of maximum optical
path penalty. Sensitivity usually takes
into account worst-case operating and end-of-life
(EOL) conditions. |
| Recombination: Combination
of an electron and a hole in a semiconductor
that releases energy, leading to light emission. |
| Refraction: The changing
of direction of a lightwave in passing
through a boundary between two dissimilar media,
or in a graded-index medium where refractive
index is a continuous function of position. |
 |
| Refractive
Index: A property of optical materials
that relates to the speed of light in the material
versus the speed of light in a vacuum. |
| Refractive Index Gradient: The
description of the value of the refractive
index as a function of distance from the
optical axis along an optical fiber diameter.
Also called refractive index profile. |
| Regenerative Repeater: A repeater, designed for digital transmission, in
which digital signals are amplified, reshaped,
retimed, and retransmitted. |
 |
| Regenerator: Synonym
for regenerative repeater. |
| Repeater: A receiver and transmitter set designed
to regenerate attenuated signals. Used to extend
operating range. |
 |
| Return
Path: A communications connection that
carries signals from the subscriber back to
the operator. The return path allows for interactive
television and on-demand services, such as pay-per-view, video on demand,
and interactive games. |
Click to Enlarge Image |
| Residual Loss: The loss of the attenuator at the minimum
setting of the attenuator. |
| Responsivity: The
ratio of a photodetector’s electrical output to its optical input in Amperes/Watt
(A/W). |
| Return Loss: See optical return
loss. |
| RF: Abbreviation for
radio frequency. Any frequency within the electromagnetic
spectrum normally associated with radio
wave propagation. |
| RF Carrier: An AM technique wherein a carrier,
with a frequency much higher than the encoded
information, varies according to the amplitude
of the information being encoded. |
| RFI: Abbreviation for radio
frequency interference. Synonym for electromagnetic
interference. |
| RGB: Abbreviation for red,
green, and blue. The basic parallel component
set in which a signal is used for each primary
color, or the related equipment or interconnect
formats or standards. |
| Ribbon Cables: Cables in which many fibers and/or copper
wires are embedded in a plastic material in
parallel, forming a flat ribbon-like structure. |
 |
| RIN: Abbreviation for relative
intensity noise. Often used to quantify the
noise characteristics of a laser. |
| Ring: A set of stations
wherein information is passed sequentially between
stations, each station in turn examining or
copying the information, and finally returning
it to the originating station. |
| Ring Network: A network topology in which terminals are connected in a point-to-point
serial fashion in an unbroken circular configuration. |
 |
| Rise Time: The time taken
to make a transition from one state to another,
usually measured between the 10% and 90% completion
points of the transition. Alternatively the
rise time may be specified at the 20% and 80%
amplitudes. Shorter or faster rise times require
more bandwidth in a transmission
channel. |
 |
| RJ: See Random Jitter. |
| RMS: Abbreviation for root
mean square. Technique used to measure AC voltages. |
| RS-250C: An ANSI recommended standard
for video transmission used to evaluate the
quality of a received picture quality. Different
requirements exist for short-haul, medium-haul, and long-haul RS-250C. Each of these
three levels is defined by the number of intermediate
processing devices and the type of path (optical
or electrical). |
| RTS: Abbreviation for request
to send. In a communications network, a signal from
a remote receiver to a transmitter for data
to be sent to that receiver. |
| RZ: Abbreviation for return
to zero. A common means of encoding data that
has two information states called ero and
ne?in which the signal returns to a rest
state during a portion of the bit period. |
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